kernel-hardening - Re: [PATCH 02/30] ARM: assembler: introduce adr_l, ldr_l and str

Follow @Openwall on Twitter for new release announcements and other news

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20170814155325.GW6321@e103592.cambridge.arm.com>
Date: Mon, 14 Aug 2017 16:53:25 +0100
From: Dave Martin <Dave.Martin@....com>
To: Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc: Mark Rutland <mark.rutland@....com>, Kees Cook <keescook@...omium.org>,
	Arnd Bergmann <arnd@...db.de>, Nicolas Pitre <nico@...aro.org>,
	Marc Zyngier <marc.zyngier@....com>,
	Kernel Hardening <kernel-hardening@...ts.openwall.com>,
	Russell King <linux@...linux.org.uk>,
	Tony Lindgren <tony@...mide.com>,
	"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>,
	Thomas Garnier <thgarnie@...gle.com>,
	Matt Fleming <matt@...eblueprint.co.uk>
Subject: Re: [PATCH 02/30] ARM: assembler: introduce adr_l, ldr_l and str_l
 macros

On Mon, Aug 14, 2017 at 04:40:55PM +0100, Ard Biesheuvel wrote:
> On 14 August 2017 at 16:32, Dave Martin <Dave.Martin@....com> wrote:
> > On Mon, Aug 14, 2017 at 01:53:43PM +0100, Ard Biesheuvel wrote:

[...]

> >> So use the above to implement the macros mov_l, adr_l, adrm_l (using ldm
> >
> > I don't see adrm_l in this patch.
> >
> 
> Oops (2)
> 
> Nico already mentioned that, and I failed to fix the commit log. I
> added it at some point, but it wasn't really useful

Thought it might be something like that.

> >> to load multiple literals at once), ldr_l and str_l, all of which will
> >> use movw/movt pairs on v7 and later CPUs, and use PC-relative literals
> >> otherwise.
> >
> > Also...
> >
> > By default, I'd assume that we should port _all_ uses of :upper16:/
> > :lower16: to use these.  Does this series consciously do that?  Are
> > there any exceptions?
> >
> 
> There aren't that many. Anything that refers to absolute symbols will
> break under CONFIG_RELOCATABLE and I haven't noticed any issues (I
> tested extensively with Thumb2)
> 
> I don't mind open coded movw/movt for relative references in code that
> is tightly coupled to a platform that guarantees v7+ so I didn't do a
> full sweep. Also, I started with 50+ patches and tried to remove the
> ones that are mostly orthogonal to the KASLR stuff.

OK, that sounds reasonable.

Cheers
---Dave

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.